首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3248915篇
  免费   269895篇
  国内免费   13761篇
耳鼻咽喉   44362篇
儿科学   104162篇
妇产科学   83180篇
基础医学   523061篇
口腔科学   87085篇
临床医学   292722篇
内科学   566066篇
皮肤病学   88455篇
神经病学   280142篇
特种医学   127554篇
外国民族医学   329篇
外科学   502004篇
综合类   100742篇
现状与发展   23篇
一般理论   2279篇
预防医学   275742篇
眼科学   74003篇
药学   220939篇
  23篇
中国医学   9317篇
肿瘤学   150381篇
  2021年   55140篇
  2020年   35195篇
  2019年   58187篇
  2018年   71164篇
  2017年   54280篇
  2016年   59830篇
  2015年   73889篇
  2014年   108123篇
  2013年   173396篇
  2012年   87972篇
  2011年   87565篇
  2010年   115612篇
  2009年   120207篇
  2008年   74124篇
  2007年   76187篇
  2006年   87234篇
  2005年   82378篇
  2004年   84573篇
  2003年   75556篇
  2002年   65270篇
  2001年   94423篇
  2000年   86965篇
  1999年   88665篇
  1998年   64314篇
  1997年   62359篇
  1996年   60117篇
  1995年   55669篇
  1994年   49945篇
  1993年   46512篇
  1992年   62366篇
  1991年   59471篇
  1990年   56570篇
  1989年   55947篇
  1988年   51614篇
  1987年   51032篇
  1986年   48133篇
  1985年   48655篇
  1984年   45279篇
  1983年   41557篇
  1982年   40683篇
  1981年   38502篇
  1980年   36201篇
  1979年   37060篇
  1978年   33756篇
  1977年   30960篇
  1976年   28464篇
  1975年   26811篇
  1974年   27586篇
  1973年   26532篇
  1972年   24650篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Coronary magnetic resonance angiography (CMRA) is a technique in clinical evolution. Current clinical applications include assessment for coronary anomalies, aneurysms, bypass graft patency, and, in experienced centers, the exclusion of proximal and multivessel coronary artery disease (CAD). As local expertise increases and more extensive multicenter data become available, additional applications will be established. CMRA promises to supplement and in some cases obviate the need for X-ray contrast angiography, and to expand our understanding of the pathophysiology of CAD. Zusammenfassung Die Magnetresonanzangiographie der Koronargefäße (CMRA) ist eine sich ständig weiterentwickelnde Technik. Etablierte Anwendungen sind zurzeit die Beurteilung von koronaren Anomalien, Aneurysmen und der Durchgängigkeit von Bypasses. Auch der Ausschluss proximaler Koronarstenosen und einer koronaren Mehrgefäßerkrankung ist in einigen spezialisierten Zentren möglich. Mit zunehmender Erfahrung der jeweiligen Anwender und der Verfügbarkeit von Ergebnissen großer multizentrischer Studien können zukünftig weitere klinische Anwendungen etabliert werden. In der Zukunft könnte die CMRA ergänzende Informationen zur Indikationsstellung einer konventionellen Röntgenangiographie bringen und in einigen Fällen diese Untersuchung sogar ersetzen. Die CMRA wird unseren Einblick in die Pathophysiologie der koronaren Herzerkrankung sicher erweitern.  相似文献   
992.
BACKGROUND: Adrenocortical carcinoma (ACC) is a rare and highly malignant tumour with a poor prognosis. Patients present with signs of steroid hormone excess (e.g., Cushing's syndrome) or symptoms due to an abdominal mass. DIAGNOSIS: In case of an adrenal mass, hormonal workup before surgery is required for differential diagnosis, perioperative management, and for follow-up. The imaging of choice is CT or MRI with MRI being of additional use when invasion of big vessels is suspected. Apart from that, the use of 18-FDG-PET is becoming increasingly established. TREATMENT: Surgical resection is the therapeutic option of choice in stages 1 - 3. In stage 4, the adrenolytic compound mitotane is part of the first-line treatment, but often needs to be combined with cytotoxic chemotherapy. Most patients will eventually have a recurrence, so adjuvant treatment (mitotane/tumour bed radiation) has to be considered in high risk patients, even if randomized controlled trials on adjuvant treatment are still lacking. STRUCTURAL PROGRESS: Several national and European structures have recently been established in order to increase our knowledge of ACC, improve therapeutic options and diagnostic procedures, and promote research. GANIMED, as a Germany-wide network of experts on adrenal diseases, has been founded allowing for improved gathering of data and joint studies. ENSAT (European Network for the Study of Adrenal Tumours) has been brought to life, aiming at European standards for therapy, diagnosis and tumour banking. Since 2003, patients can be enrolled in the German ACC Registry. France and Italy have also developed a central registry to collect nationwide data from patients with ACC. For the first time, patients with metastatic/unresectable ACC can participate in a prospective controlled randomized trial comparing two different cytotoxic chemotherapy regimes (FIRM-ACT).  相似文献   
993.
BACKGROUND: Radioiodine therapy (RIT) combined with glucocorticoids is an effective therapy for Graves' disease, but it is debatable whether glucocorticoids should be applied in patients without Graves' ophthalmopathy (GO). METHODS: The effect of 0.4 - 0.5 mg prednisone every second day over a period of 5 weeks after RIT was monitored over a follow-up period of at least 12 months after RIT. A questionnaire was sent to 186 consecutive patients without GO concerning eye symptoms after RIT. 148 patients (80 %) answered. If eye symptoms had occurred after RIT, additional clinical examination was carried out at our outpatient clinic. The primary endpoint was the absence or onset of GO within the first year after RIT. RESULTS: Within 12 months after RIT the examination confirmed GO in 5 out of 148 patients (3.4 %). In all cases the symptoms were transient. No adverse reaction to the use of prednisone after RIT was noted. CONCLUSIONS: The risk of new GO in the first year after RIT was low and the clinical course of GO was mild when RIT was combined with a low-dose glucocorticoid regimen. Preventive administration of glucocorticoids can therefore be recommended in patients with Graves' disease even without evident GO.  相似文献   
994.
The present study compared four different sites and conditions for the measurement of maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) in 38 spontaneous breathing tracheotomised patients. Of the patients, 28 had chronic obstructive pulmonary disease (COPD). The four different conditions were: 1) through a cuff inflated cannula (condition A); 2) through the mouth with a deflated cannula (condition B); 3) through the mouth with a phonetic uncuffed cannula (condition C); and 4) through the mouth after stoma closure (condition D). Five trials in each condition were performed using a standardised method. The measurement of both MIP and MEP differed significantly depending on the condition of measurement. MIP taken in condition A was significantly higher when compared with conditions B, C and D. MEP in condition A was significantly higher when compared with condition B and D. In condition A the highest frequency of the best measurement of MIP and MEP was observed at the fourth and fifth effort, respectively. The same results were obtained after the selection of only COPD patients. In conclusion, respiratory muscle assessment differs significantly depending on measurement condition. Measurement through inflated cannula tracheotomy yields higher values of both maximal inspiratory and maximal expiratory pressure.  相似文献   
995.
996.
997.
目的探讨颗粒松质骨压紧植骨全髋关节置换术(THA)治疗髋臼骨折继发创伤性髋关节炎的疗效。方法1998年12月-2005年5月,对15例髋臼骨折继发创伤性髋关节炎患者行颗粒松质骨压紧植骨THA,所有患者髋臼假体均采用骨水泥固定,颗粒骨均取自体骨,术后24h后开始被动活动,3个月后开始全负重锻炼。临床随访采用Harris髋关节评分(HSS)系统评分,对任何原因引起髋臼假体翻修均视为临床失败。根据Conn等影像学评价法观察颗粒骨长人情况,根据DeLee的三区法测量臼杯、骨水泥与移植骨间的界面宽度,臼杯的移位程度则依据其相对于泪点间线的距离而定。结果14例患者获得平均4.3年(1.0-7.5年)随访,HHS评分由术前平均42分(10-62分)提高到随访结束时平均84分(58-98分)。1例髋部有轻度疼痛,无患者行翻修手术。大部分髋部恢复了其正常的旋转中心,仅有2例高出对侧0.8 mm。大多数患者影像学表现稳定,2例在Ⅰ区和Ⅲ区出现进行性增宽的透亮带,1例在Ⅲ区出现非进行性增宽的透亮带。1例臼杯假体在术后7年出现明显移位(6 mm),但并没有行翻修手术。结论颗粒骨压紧植骨技术作为一种生物学髋臼重建方法,其联合THA治疗髋臼骨折后继发创伤性关节炎伴髋臼缺损的疗效令人满意,能够恢复髋关节的正常解剖和功能活动。  相似文献   
998.
999.
The aim of the study was to investigate whether hypothermic oxygenated liver perfusion after cold liver preservation resuscitated metabolic parameters and whether this treatment had a benefit for liver viability upon reperfusion.
We preserved rat livers either by cold storage (UW) for 10 h, or by perfusion for 3 h (oxygenated modified UW) after 10 h cold storage. We assessed viability of livers after preservation and after ischemic rewarming + normothermic reperfusion ex vivo . Ten hour cold storage reduced mitochondrial cytochrome oxidase and metabolically depleted the livers. Oxygenated perfusion after cold storage resulted in uploaded cellular energy charge and oxidized mitochondrial cytochrome oxidase. Reperfusion after 10 h cold storage increased formation of superoxid anions, release of cytosolic LDH, lipid peroxidation, caspase activities and led to disruption of sinusoidal endothelial cells. In contrast, reperfusion after 10 h cold storage + 3 h hypothermic oxygenated perfusion resulted in no changes of lipid peroxidation, bile flow, energy charge, total glutathione, LDH release and of caspase activation, as compared to fresh resected livers.
This study demonstrates, that a metabolically depleted liver due to cold storage can be energy recharged by short-termed cold machine perfusion. The machine perfused graft exhibited improved viability and functional integrity.  相似文献   
1000.
Antibody-mediated rejection (AMR) after liver transplantation is recognized in ABO incompatible and xeno-transplantation, but its role after ABO compatible liver transplantation is controversial. We report a case of ABO compatible liver transplantation that demonstrated clinical, serological and histological signs of AMR without evidence of concurrent acute cellular rejection. AMR with persistently high titers of circulating donor specific antibodies resulted in graft injury with initial centrilobular hepatocyte necrosis, fibroedematous portal expansion mimicking biliary tract outflow obstruction, ultimately resulting in extensive bridging fibrosis. Immunofluorescence microscopy demonstrated persistent, diffuse linear C4d deposits along sinusoids and central veins. Despite intense therapeutic intervention including plasmapheresis, IVIG and rituximab, AMR led to graft failure. We present evidence that an antibody-mediated alloresponse to an ABO compatible liver graft can cause significant graft injury independent of acute cellular rejection. AMR shows distinct histologic changes including a characteristic staining profile for C4d.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号